Class AttachProvider
An attach provider is a concrete subclass of this class that has a zero-argument constructor and implements the abstract methods specified below.
An attach provider implementation is typically tied to a Java virtual machine implementation, version, or even mode of operation. That is, a specific provider implementation will typically only be capable of attaching to a specific Java virtual machine implementation or version. For example, Oracle's JDK implementation ships with provider implementations that can only attach to Oracle's HotSpot virtual machine. In general, if an environment consists of Java virtual machines of different versions and from different vendors then there will be an attach provider implementation for each family of implementations or versions.
An attach provider is identified by its name and
type. The name is typically, but not required to
be, a name that corresponds to the VM vendor. The Oracle JDK implementation,
for example, ships with attach providers that use the package name "sun"
(for historical reasons). The
type typically corresponds to the attach mechanism. For example, an
implementation that uses the Doors inter-process communication mechanism
might use the type "doors". The purpose of the name and type is to
identify providers in environments where there are multiple providers
installed.
AttachProvider implementations are loaded and instantiated at the first
invocation of the providers method. This method
attempts to load all provider implementations that are installed on the
platform.
All of the methods in this class are safe for use by multiple concurrent threads.
- Since:
- 1.6
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Constructor Summary
ConstructorsModifierConstructorDescriptionprotectedInitializes a new instance of this class. -
Method Summary
Modifier and TypeMethodDescriptionAttaches to a Java virtual machine.abstract VirtualMachineAttaches to a Java virtual machine.abstract List<VirtualMachineDescriptor> Lists the Java virtual machines known to this provider.abstract Stringname()Return this provider's name.static List<AttachProvider> Returns a list of the installed attach providers.abstract Stringtype()Return this provider's type.
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Constructor Details
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AttachProvider
protected AttachProvider()Initializes a new instance of this class.
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Method Details
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name
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type
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attachVirtualMachine
public abstract VirtualMachine attachVirtualMachine(String id) throws AttachNotSupportedException, IOException Attaches to a Java virtual machine.A Java virtual machine is identified by an abstract identifier. The nature of this identifier is platform dependent but in many cases it will be the string representation of the process identifier (or pid).
This method parses the identifier and maps the identifier to a Java virtual machine (in an implementation dependent manner). If the identifier cannot be parsed by the provider then an
AttachNotSupportedExceptionis thrown. Once parsed this method attempts to attach to the Java virtual machine. If the provider detects that the identifier corresponds to a Java virtual machine that does not exist, or it corresponds to a Java virtual machine that does not support the attach mechanism implemented by this provider, or it detects that the Java virtual machine is a version to which this provider cannot attach, then anAttachNotSupportedExceptionis thrown.- Parameters:
id- The abstract identifier that identifies the Java virtual machine.- Returns:
- VirtualMachine representing the target virtual machine.
- Throws:
AttachNotSupportedException- If the identifier cannot be parsed, or it corresponds to to a Java virtual machine that does not exist, or it corresponds to a Java virtual machine which this provider cannot attach.IOException- If some other I/O error occursNullPointerException- Ifidisnull
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attachVirtualMachine
public VirtualMachine attachVirtualMachine(VirtualMachineDescriptor vmd) throws AttachNotSupportedException, IOException Attaches to a Java virtual machine.A Java virtual machine can be described using a
VirtualMachineDescriptor. This method invokes the descriptor'sprovider()method to check that it is equal to this provider. It then attempts to attach to the Java virtual machine.- Parameters:
vmd- The virtual machine descriptor- Returns:
- VirtualMachine representing the target virtual machine.
- Throws:
AttachNotSupportedException- If the descriptor'sprovider()method returns a provider that is not this provider, or it does not correspond to a Java virtual machine to which this provider can attach.IOException- If some other I/O error occursNullPointerException- Ifvmdisnull
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listVirtualMachines
Lists the Java virtual machines known to this provider.This method returns a list of
VirtualMachineDescriptorelements. EachVirtualMachineDescriptordescribes a Java virtual machine to which this provider can potentially attach. There isn't any guarantee that invokingattachVirtualMachineon each descriptor in the list will succeed.- Returns:
- The list of virtual machine descriptors which describe the Java virtual machines known to this provider (may be empty).
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providers
Returns a list of the installed attach providers.An AttachProvider is installed on the platform if:
- It is installed in a JAR file that is visible to the defining
class loader of the AttachProvider type (usually, but not required
to be, the
system class loader). - The JAR file contains a provider configuration named
com.sun.tools.attach.spi.AttachProviderin the resource directoryMETA-INF/services. - The provider configuration file lists the full-qualified class name of the AttachProvider implementation.
The format of the provider configuration file is one fully-qualified class name per line. Space and tab characters surrounding each class name, as well as blank lines are ignored. The comment character is
'#'(0x23), and on each line all characters following the first comment character are ignored. The file must be encoded in UTF-8.AttachProvider implementations are loaded and instantiated (using the zero-arg constructor) at the first invocation of this method. The list returned by the first invocation of this method is the list of providers. Subsequent invocations of this method return a list of the same providers. The list is unmodifiable.
- Returns:
- A list of the installed attach providers.
- It is installed in a JAR file that is visible to the defining
class loader of the AttachProvider type (usually, but not required
to be, the
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